1. Field of the Invention
The present invention relates to a metal bonded drilling and boring tool.
2. Description of the Related Art
In the case of drilling a hole in a hard material such as a stone, concrete, and tile, it is conventionally general to mount a diamond core bit on an electric drill. Further, in the case of boring the drilled hole to enlarge its diameter, a so-called cemented carbide bar formed of cemented carbide alloy or high-speed steel is mounted on a trimmer, router, or hand grinder. In this mounted condition, the cemented carbide bar is rotated at a high speed of 10,000 rpm or more. As another conventional boring method, a shafted abrasive wheel or an electrodeposited bar formed by electrodeposition of diamond abrasive grains on a steel bar is mounted on a trimmer, router, or hand grinder. In this mounted condition, the shafted abrasive wheel or the diamond electrodeposited bar is rotated at a high speed.
Thus, the boring is performed by using another tool such as a cemented carbide bar after drilling a hole by using a diamond core bit. Accordingly, the drilling tool must be exchanged to the boring tool before boring, causing a reduction in workability. Although a ceramics board containing a cement material may be bored by using a cemented carbide bar, the life of the cemented carbide bar is very short in this case. Further, although a stone or tile may be bored by using a shafted abrasive wheel or diamond electrodeposited bar, such a tool has a characteristic of undergoing a large cutting resistance, causing a reduction in life. Further, such a large cutting resistance causes exertion of a large force on the shaft of such a tool. As a result, the tool may be broken before deterioration in cutting performance.